Air classifier



April 17, 1928.

A. H. STEBBINS AIR CLASSIFIER Filed Oct. 14. 1926 ATTORNEY Patented Apr.17, 1928.

- Lu N1 ran sums P A -T- Ewr F-FICE l ALBERT .srranms,-.or LOS ANGELES,CALIFORNIA.

AIR CLASSIFIED.

a ncationmed were 14, 1926. semi 1x0441 547.

This invention relates to air classifiersiof the type in whichseparation ofthe 'materials-is effected by subjectingthe materials tothe action of air currents that carry off the lighter particles.

It has been proposed heretofore to classify materials by passing airupwardly through the materials traveling along a screen or otherapertured surface so that the air will pickup the finer particleswithout carrying ofithe coarser particles. 1 I

These proposed air classifiers workyery well when employed to removefine dust-like particles from relatively large coarse particles, butwhenv the/materials being treated are very fine and differ only slightlyin size, it is necessary to subject them timeand 'time'againto theseparating action of'gent-le air currents in order to effect the desiredclassification.

. The separation of these fine, dust-likeparticles can be effectedby'advancing: them over the surface ofa long screen or aperturedsupporting surface having gentle currents-of air passing upwardlythrough the apertures to carryofi' the lighter particlesybuta screen orsupporting surface having a sufiicient length to effect a completeclassification of the materials -may occupy an excessive amount of floorspace. a

The present invention therefore contemplates a construction in which theclassifying chamber is given the form of-a spiral conduit and isprovided with an apertured supporting surface that is 'constructedtoform a spiral slide-way along whiclrthe ma-terials'to be treated travel.This spirally shaped classifier is supported in an upright positionandtherefore requires only a small amount of floor-space. I

One of 'the'features of the invention -resides in theconstructionwherebyair is exhausted'from the spiral classifying chamberabove the apertured surface at a number of :points along the spiralchamber. 1

Another feature of the invention resides Kin the construction wherebyair under pressure is forced upwardly through the apertures of thespiral supporting surface.

'Other features of the invention and novel combination of parts inaddition "to-the above will be hereinafter described in con- 'nection'with the accompanying-drawings which illustrate good practical forms ofthe invention. i

structed in accordance sectional View through classifier of Fig. 1;:and

- matter of. thepresent inven be varied :as

sirable because the therefore preferably constructed so that In the,drawings Fig. 1 :is .a side-elevation, -with. parts-bro- .kenaway, of.a spiral air classifier 0on Withthe present invention;

Fig. '2. onansenlargedscale is atransverse sectional 1 View through theclassifier of ,F 1g. 1;

Fig. 3 on ;an enlarged scale-is a vertical .a. portion of the F'g i isa. sectional" view similar to, Fig.

3,; but/shows ;a modified construction.

The air classifier forming the subject tionv .is designed more.particularly forsuse in treating fine llHSt-Ilike particles, and ;as@above pointed out,

in order tovefi'ectively separate theseisfine particles it .is necessaryto subject them repeatedly to itliecseparating action-of jgentleair-currents. This-isiidone' in accordance with 1 the present inventionby .causingithe materials to be treated totravelalon a spirally woundmaterial supporting-s11 ace or slide-way which is provided withapertures,nand .air. is caused .-to pass upwardly through the aperturesand materials upon the slide-way. t0 carry off 1 the lighter :par-

holes.

porting structure for the spiral casing "10 and it also constitutesasatisfactory means for exhausting air from the casing; as -willpresently appear it -is ':apparent, however,

that other meansmight be provided :-for supporting'the spirally disposedcoils of the casing-an 1 air currentsvwith-in this casing.

for producing the desired rising The casing-1 01m construotedto form aclosure above or about'the aperturedma- (serial-supporting surface#12and the portion of the casing which is disposedabove. the supportingsurface or slide-way 12 constitutes a --settling chamber. .The casing isit flares outwardly: as it extends upwardlyxfrom the surface 12 toincreasethe-cizeof the setin a thin layer so portion of tling chamber,as will be apparent from the vertical sectional View ofFig. 3, whereinthe casing is shown as formed of the wide upper wall 13, the narrowlower walll tand the side wa-ll15.

The inclination or pitch of the-spirally wound casing 10 is preferablysuch that when the casing is supported in a position the materials willslide downwardly along the spiral slide-way 12 under the in-.

fiuence of gravity assisted by the action of theair passing upwardlythrough the aper- -tures16 of the surface 12.

The materials to be treated may be delivered to the upper the Classifierby a hopper 17 having the sliding gate 18 that may be adjusted to varythe rate of feed, and the rate at which the materials-are supplied tothe classifier is preferably will slide rapidly along the floor-plate12that all particles are repeatedly subjected to the lifting action of theair. e v

The separation of the materials is effected by causing air to passupwardly through the apertures '16 and materials traveling over theapertures to pick up the lighter particles. These rising air currentsmay "produced by exhausting air from the spiral casing 10 at a numberofpoints along its length, and this is accomplished in the constructionshown by providing the passages or elongated slots 19 in the walls ofthe pipe 11 sothat when air is exhausted from the pipe 11 a suctionvwill be produced within the casing 10 to .draw. air upwardly The slots19 pref-' through theapertures 16.

the upper wall 13' The rising air currents within the casing 10 may befurther. produced by providingthe air passage 20 formed between theapertured surface portion 2 1 of this pipe '12 and the lower wall 14,and air under pressure may be forced into this assage near the lower endof the classifier by the pipe 21 that is connected to a blast fan '22. I

*The discharge end of erably flattened out as the pipe 21 isprefconnecting the upper to a suction fan 25. The lighter particleswhich are picked up from the pipe 11 by from the'surface 12 "by the aircurrents arecarried through, the openings 19 into the pipe 11, and suchparticles as may settle in this :pipe are discharged through its reduced7 7 lower end 25, while the particles that remain suspended in the alrare carried off by the suction means. The heavier particles that are notpicked up by the air are directed by the slide-way 12 into thereceptacle 26.

' It may be desirable to prevent the air within the casing 10 fromtraveling lengthplates 27 to each other and as having one slot 19 1n thespace formed between a pair of baflie vertical such that the materialsat 23 so that it will extend into the passage 20. Air is exhaustedslide-way forwise of this spiral casing. This may be done by mounting inthe casing the battle which are constructed to fit the upper portion ofthe casing. The baffie plates are shown as disposed at angles ofwithplates. As aresult of this construction the air rises more or lessvertically within the upper portion of the casing forming'the settlingchambers.

.In vthe modified construction of Fig. i the means for delivering air tothe under side of the apertured surface under pressure is omitted, andthe suction produced within the casing 10 serves to draw air from theatmosphere up through the apertures 16 of the material supportingsurface 12.

Through the use of the spiral construction forming the subject matter ofthe present invention the materials being treated are caused to travelover an apertured surface 12 of any desired length. In this manner theparticles are repeatedly subjected to the separating action of gentleair currents, and

the classification of thematerials is effected in a simple compactdevice that requires only a small amount of floorspace.

What is claimed is 1. A spiral classifier, comprising in combination, avertically disposed pipe having air inlet openings in its walls, aclosed casing wound spirally around the pipe to communicate with saidopenings and constructed to form a spiral classifying chamber, anapertured floor-plate for the casing extending spirally around thecentral pipe and constructed so that the materials to be treated willslide down the floor-plate, means for delivering the materials to betreated to the upper end of the spiral casing, and means for exhaustingair from said pipe to draw air into the spiral chamber through theapertures in the floor plate and from the chanr her into the centralpipe to cause the air to pick up and carry into the central pipe thelighter particles traveling along the floorplateu 2. A classifier,comprising in combination, a spirally wound closed casing or conduitthat is supported in an upright position and constructed to form avspiral classifying chamber, an apertured floor-plate for the casing andconstructed to form a spiral the materials, means for delivering thematerials to be treated to the u per end of the casing to pass downwardltherein, and means for exhausting air from the casing at a multiplicityof points along its length to draw air upwardly through the apertures inthe floor-plate to cause the air to pick up the lighter particlestraveling along the floor-plate.

3. A classifier for classifying fine, dustlike materials, comprising incombination,

loo

a spirally wound closed casing or conduit that is supported in anupright position and constructed to form a spiral classifying chamber,an apertured floor-plate for the casing and constructed to form a spiralslideway for the materials, means for delivering the materials to betreated to the upper end of the casing to pass downwardly therein, meansfor forcing air upwardly through the apertures in the floor-plate tocause the air to pick up the lighter particles traveling along thefloor-plate, and means for extracting ,from the conduit the air in whichthe lighter particles are suspended.

4. A classifier, comprising in combination, a vertically disposed pipe,a closed casing wound spirally around the pipe and constructed to form aspiral classifying chamher having air passages communicating with theinterior of said pipe, an apertured floorplate for the casing extendingaround said pipe and constructed to form a spiral slideway for thematerials, means for delivering the materials to be treated to the upperend of the casing, and means for producing air currents passing upwardlythrough said apertures and from the spiral casing into said pipe to pickup the lighter materials traveling along said slide-way.

5. A classifier, comprising in combination, a spirally wound closedcasing or conduit that is supported in an upright position andconstructed to form a spiral classifier, an apertured floor-platesupported in spaced relation to the under side wall of the casing orconduit and arranged to form a spiral slide-way for the materials and toprovide an air passage below the floor-plate, means for delivering thematerials to be treated to the upper end of the casing to passdownwardly therein, means for forcing air into the air passage below thefloor-plate to produce air currents passing upwardly through theapertures of the floor-plate and which serve to pick up the lightermaterials sliding along the floor-plate, and means for exhausting theair in which the lighter particles are suspended from the conduit at aseries of points along its length. I

6. Aclassifier, comprising in combination, a spirally wound closedcasing or conduit that is supported in an upright position andconstructed to form a spiral classifying chamber, an aperturedfloor-plate for the casing and constructed to form a spiral slide-wayfor the materials, means for exhausting air from the casing'above thefioorplate at a multiplicity of points along the spiral casingto drawair upwardly through said apertures and cause the air to pick up andcarry off the lighter particles traveling along the floor-plate, andbattle plates mounted in the spiral casing to prevent the air currentswithin the casing from traveling lengthwise of the spiral casing.

7. A classifier for classifying fine materials, comprising incombination, a spirally wound closed casing or conduit that is supportedin an upright position and constructed to form a spiral classifyingchamher in which the materials beingtreated are confined from theatmosphere, an apertured floor-plate for the casing and constructed toform a spiral slide-way for the materials and positioned to provide asettling space in the chamber above the floor-plate, means fordelivering the materials to be treated to the u per end of the casing topass downward Y therein, and means for producing air currents that passupwardly through the apertures of the floor-plate into said chamber topick up the lighter particles traveling along the floor-plate andoperable also to exhaust air from said chamber to carry ofi the lighterparticles.

In testimony whereof, I have signed my name to this specification.

ALBERT H. STEBBINS.

